First create a free account, then simply upload your CSV files to combine by clicking +New > File Upload > Browse to select files from your machine. You can zip your file to save time uploading. Don't want to download your files? No problem. Click the Link option in the lower part of the upload box and provide publicly accessible URL to your CSV files or to a zip of CSVs.
Next your CSV files will automatically upload (and unzip if necessary). For exceptionally large files you'll see a loading bar while the file parses.
Use the blue check boxes to select your CSV files to combine. Once 2+ files are selected, hit Combine and a box will appear asking to name your new file containing the combined data. Once a name is provided, click Save and your files will be combined. It's that easy!
Combine files requires that the files have the same number and types of columns. Header rows will automatically be detected as part of the combine process and removed from the data.
Once complete, click on the newly created file in your Library to view the CSV file online. The viewer will open a spreadsheet in a new browser tab for viewing. Here you can filter, search, or create pivot tables with your CSV.